Find out the total convective heat transfer rate from the board in Example 2B.2 (solve the bolded part) Example 2B.2: A 15-cm by 15-cm circuit board is being cooled by air. It is dissipating 890 W/m² of heat to the air from its top surface. The air approaches the circuit board at 25 °C with a velocity of 6 m/s. Determine the surface temperature of the circuit board at the end of the board. Assume the flow to be turbulent at the leading edge of the board since the electronic components are expected to act as turbulators. For air properties evaluations assume a film temperature of 35 °C. Given: Circuit board geometry – length, L = 0.15 m, width, W = 0.15 m %3D Convective heat flux to air, q" = 890 W/m² Free-stream temp., T, = 25 °C. Free-stream velocity, U» = 6 m/s %3D Assumption: Steady state. Only mode of heat transfer from the board is convection. Film temperature is T; = 35°C. Properties are considered constant and uniform. Flow is turbulent. Air is an ideal gas.

5.10 A flaked cereal is of thickness 2L = 1.2 mm. The density, specific heat, and thermal conductivity of the flake are p = 700 kg/m³, cp = 2400 J/kg K, and k = 0.34 W/mK, respectively. The product is to be baked by increasing its temperature from T₁ = 20°C to T, = 220°C in a convec- tion oven, through which the product is carried on a con- veyor. If the oven is L₁ = 3 m long and the convection heat transfer coefficient at the product surface and oven air temperature are h = 55 W/m² K and T. = 300°C, respectively, determine the required conveyor velocity, V. An engineer suggests that if the flake thickness is reduced to 2L = 1.0 mm the conveyor velocity can be increased, resulting in higher productivity. Determine the required conveyor velocity for the thinner flake. 2L = 1.2 mm Conveyor belt Cereal product V L₂ Oven h = 55 W/m².K T_= 300°C

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Due higher viscosity, the heat-transfer coefficient of moving liquid hydrocarbons is generally higher than that of moving water Select one: O True O False The proper strategy to enhance heat transfer of a heat exchanger is trying to increase the heat transfer coefficient of the side with the lower heat resistant. Select one: O True O False For the universal 3-D heat transfer equation (see topic 7 in URCourses notes), we have to simplify by eliminating terms that are zero or near zero first, and then we can only use numerical methods (such as finite difference) to solve those problems. Select one: O True O False